The present invention relates generally to the storage and retrieval of data within magnetic media. In particular, the present invention relates to the placement of shorting shields around the main pole of a perpendicular writer.
A typical transducing head consists of two portions: a writer portion for storing magnetically encoded information on magnetic media and a reader portion for retrieving the magnetically encoded information from the media. The magnetic media is typically organized into tracks which are further organized into bit fields. The MR sensor travels along a track in close proximity to the media to detect differences in the stored magnetic flux between bit fields. Changes in the magnetic flux from one bit field to another result in a corresponding resistivity change and consequent voltage output from the MR sensor. Since it is the changes from one bit field to another that are detected and result in data output; it is critical that those transitions be sharp, that is, as narrow as possible. Sharp transitions, as well as other characteristics for successful reading, are not controlled by the reader, but instead by the writer and the process used to encode the data within the magnetic media.
A perpendicular writer typically consists of a main pole with at least one adjacent return pole separated from each other at an air bearing surface. Additionally, the magnetic poles are connected by a back via at a region away from the air bearing surface. Positioned between the two poles are one or more layers of conductive coils encapsulated by electrically insulating layers. To write data to the magnetic media, a time varying electrical current, or write current is caused to flow through the conductive coils.
The write current produces a time varying magnetic field in the magnetic poles called the write field. The magnetic poles, back via and the magnetic media are part of a magnetic flux path, which is also referred to as a reluctance circuit. The write field passes from the main pole into the magnetic media, thereby writing to a recording layer within the media. Residual magnetic flux from the main pole closes the reluctance circuit via a soft underlayer of the magnetic media. As magnetic flux passes through recording layer, thereby closing the reluctance circuit through soft underlayer, recorded bits can be destabilized resulting in the information stored in the recording layer being erased.
Recent years have seen a considerable increase in data storage densities. Generally, the storage capacity of a magnetic data storage and retrieval device is increased through use of magnetic media having an increased areal density. Areal density is the number of units of data stored in a unit area of the media. Areal density is determined by two components of the magnetic media: the track density (the number of data tracks per unit width of the magnetic media) and the linear density (the number of units of data stored per unit of length of the data track). To increase the areal density of a magnetic media one must increase the linear density and/or the track density of the magnetic media.
Increases in areal density demand that writers must write to smaller bit fields with increasing flux density. One problem with conventional perpendicular writers is the effect of the write field on adjacent tracks and bit fields. The process of writing one bit field may cause erasure of the magnetic data stored both to the side in adjacent tracks or to the adjacent bit fields in front or behind the write head. That portion of the write field that causes unwanted erasure is referred to as erasure field. There remains a continuing need in the art for improved perpendicular writers with reduced erasure fields.